"PHYLOGENETICALLY DISTINCT"

Somehow I missed obelisks. Well, I suppose everyone missed it — or them. Discovered in human gut and oral bacteria, researchers recently found these previously unknown and difficult to classify, well, things.

Something like a virus, researchers say these bits of RNA are phylogenetically distinct, meaning they sit alone on their own novel branch of the evolutionary tree. The research team published an article highlighting that these weird, living/non-living things are “without detectable similarity to known biological agents.” That’s a pretty big deal and pretty interesting.

As you would expect from them, a team of microbiologists at Stanford were pouring over a database from RNA sequences isolated out of human waste. A cluster of these things was found alongside a common bacteria called Streptococcus sanguinis. If we took a swab of your mouth we'd probably be able to isolate some of that bacteria among your oral flora and perhaps some of these obelisk guys, too.

We’re told obelisks resemble viroids: infinitesimal circular fragments of single-strand RNA. Obelisks differ in both shape and structure, however. Obelisks are not flat circles, like viroids, but are rolled into a rod and lack a virus-like protein coat, making them perhaps the simplest self-replicating chunks of genetic material we know of. Their RNA sequences also do not match known viroid sequences and they are also the first viroid-like things to be detected in bacterial cells, rather than in more complex organisms.

Being such a tiny and efficient form of self-replicating material, has led folks to question why the world isn’t teaming with these things. But it may in fact be teeming with them. Viroids are nearly ubiquitous throughout the plant world and now that microbiologists have their eyes open for these viroid-like obelisks it seems likely they’ll be found all over the place.

The real question is how these things will be classified. As you’ll notice I keep referring to them as “things” because, like so much of our world, obelisks seem to defy conventional categorization. Obelisks do not eat or regenerate or mate but they do reproduce and as such blur the line between life and non-life. So it will be interesting to see where this phylogenetically distinct virus-like non-virus will land.